Lithium ion battery positive electrode slurry and preparation method thereof

Abstract

The present invention relates to the technical field of positive electrode slurries, and specifically discloses a positive electrode slurry for lithium ion batteries and a preparation method thereof. The positive electrode slurry for lithium ion batteries comprises the following components: by weight, 32 to 40 parts of positive electrode material, 4 to 5 parts of conductive agent, 4 to 5 parts of binder, 0.002 to 0.0025 parts of photoinitiator, 25 to 35 parts of deionized water, and 10 to 12 parts of N-methylpyrrolidone. The preparation method of the positive electrode material is: adding tetrabutyl titanate to ethanol, adding NCM811 particles, ultrasonically dispersing evenly, adding a surface modifier aqueous solution, stirring evenly, steaming to a paste, freeze-drying, and heat-drying to obtain a crude precursor; the crude precursor is heat-treated to obtain a positive electrode material. In the present application, the positive electrode material is obtained by modifying the NCM811 particles and combining a binder of a specific component, thereby effectively improving the electrochemical performance of the positive electrode slurry.

Description

Technical Field

[0001] The invention relates to the technical field of positive electrode slurry, and specifically discloses a positive electrode slurry for a lithium ion battery and a preparation method thereof. Background Art

[0002] Lithium-ion battery is a common secondary battery with advantages such as high energy density and environmental friendliness. It is widely used in portable electronic products, automotive power systems, energy storage systems, etc. Among them, the positive electrode material is one of the key components of lithium-ion batteries and directly affects the performance of lithium-ion batteries.

[0003] The positive electrode materials of lithium-ion batteries generally include positive electrode main materials, conductive agents, binders, etc. Among them, the positive electrode main materials ensure the basic conductivity, the binder can increase the binding force of the positive electrode layer, and the conductive agent can optimize the charge transfer process at the battery interface. Among the positive electrode main materials, high nickel layered oxides have become one of the best choices due to their advantages such as low cost and high specific capacity. However, it still has the problem of poor stability of cyclic electrical performance. During the cycle, one is that the interface impedance increases and the electrical performance decreases; the other is that there are deep lithium removal defects, parasitic side reactions occur between the surface and the electrolyte, the positive electrode is corroded, and the particles crack, causing safety problems. Therefore, it is necessary to further improve the electrical cycle stability of the positive electrode main material. At the same time, in the prior art, the binder generally uses polyvinylidene fluoride (PVDF), but it is hard, and auxiliary agents need to be added during the slurry mixing process, and there are problems such as powder falling off, which leads to reduced electrical performance and safety.

[0004] In summary, it is of great significance to solve the above problems and prepare a positive electrode slurry for lithium-ion batteries. Summary of the invention

[0005] The object of the present invention is to provide a lithium ion battery positive electrode slurry and a preparation method thereof to solve the problems raised in the above background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: A positive electrode slurry for a lithium ion battery, characterized in that the positive electrode slurry for the lithium ion battery comprises the following components: by weight, 32 to 40 parts of positive electrode material, 4 to 5 parts of conductive agent, 4 to 5 parts of binder, 0.002 to 0.0025 parts of photoinitiator, 25 to 35 parts of deionized water, and 10 to 12 parts of N-methylpyrrolidone.

[0007] Further preferably, the preparation method of the positive electrode material comprises the following steps: adding tetrabutyl titanate to ethanol, adding NCM811 particles, ultrasonically dispersing uniformly, adding a surface modifier aqueous solution, stirring at 40-45°C for 1-2 hours; stirring and steaming at 60-65°C until a paste, freeze-drying, and heat-baking at 70-80°C for 1-2 hours to obtain a crude precursor; heat-treating the crude precursor to obtain a positive electrode material.

[0008] In this scheme, a titanium dioxide precursor containing a surface modifier is coated on NCM811 particles, and then heat-treated and calcined, so that nano-titanium dioxide and carbon containing nitrogen and boron are coated on the surface of NCM811 particles as a protective layer, effectively protecting its structural stability and effectively increasing the cycle stability of electrical performance. Compared with the single titanium dioxide coating, the simultaneous introduction of carbon containing nitrogen and boron can improve the lithium ion diffusion efficiency, reduce the charge transfer resistance, and thus improve the cycle stability of electrical performance.

[0009] Further preferably, the raw materials of the crude precursor include the following components: 10 parts of NCM811 particles, 0.3-0.35 parts of tetrabutyl titanate, 160-200 parts of ethanol, 0.1-0.12 parts of surface modifier, and 8-12 parts of deionized water.

[0010] Further preferably, the heat treatment process is: heat treatment at 500-600°C for 4-5 hours in an Ar-3% O2 ​​atmosphere; replacing the Ar atmosphere; and then replacing the Ar-5% H2 atmosphere at 680-700°C for 2-3 hours to obtain the positive electrode material.

[0011] Further preferably, the preparation method of the surface modifier comprises the following steps: adding glucosamine and epoxypyridine to ethanol in sequence, stirring and reacting at 78-82°C for 6-8 hours, and purifying to obtain the surface modifier; wherein the mass ratio of glucosamine to epoxypyridine is 1:(2.25-2.3).

[0012] In this scheme, compared with the direct use of glucosamine, the epoxypyridine grafted modifier is used to make it contain nitrogen and boron, which can increase the defect sites of carbon, so that the positive electrode material has a higher discharge specific capacity and rate capacity. At the same time, boron and titanium can effectively increase the structural strength of the positive electrode material, thereby delaying the generation of internal cracks in the particle cycle process, thereby improving the cycle attenuation rate and improving the cycle stability of electrical performance.

[0013] Further preferably, the binder comprises modified gelatin, modified polyvinylidene fluoride, and polyethylene glycol diacrylate in a mass ratio of (2-2.5):1.5:(0.5-1); the modified polyvinylidene fluoride is PVDF-g-POEM.

[0014] In this scheme, compared with the common PVDF as a binder, the scheme uses modified gelatin with photosensitivity as the main body, and modified polyvinylidene fluoride with amphiphilicity as the secondary body, and polyethylene glycol diacrylate is added to form a ternary binder. The ternary binder can produce photocrosslinking, which can be pre-photocrosslinked in the subsequent positive electrode preparation process, thereby inhibiting the migration caused by high-temperature drying, increasing the adhesion between the electrode slurries, inhibiting the de-powdering, and reducing the resistance of the electrode. In this way, the electrical performance and cycle stability of the positive electrode are improved.

[0015] Further preferably, the preparation method of the modified gelatin comprises the following steps: (1) adding gelatin and epoxy pyridine to ethanol in sequence, stirring and reacting at 78-82°C for 6-8 hours, purifying, and obtaining pyridyl gelatin; (2) adding pyridyl gelatin to phosphate buffer solution and stirring evenly, adding methacrylic anhydride dropwise, stirring and reacting at 40-45°C for 2-3 hours, purifying, and obtaining modified gelatin; Among them, the mass ratio of gelatin and epoxy pyridine is 1: (0.35~0.4); in the modified gelatin, the mass ratio of pyridyl gelatin and methacrylic anhydride is 1: (0.6~0.65).

[0016] In this scheme, gelatin is grafted with epoxypyridine and methacrylic anhydride in sequence, so that its surface contains boron and pyridine groups, thereby improving the thermal stability of the positive electrode, increasing the mobility of lithium ions, and thus improving the electrical performance. The grafting of methacrylic anhydride makes it photo-crosslinkable, which can inhibit migration during high-temperature drying, inhibit unevenness in the electrode sheet, and reduce internal resistance.

[0017] Further preferably, the preparation method of epoxypyridine comprises the following steps: adding 2-ethoxypyridine-5-boric acid and 3-(4-glycidylbutoxy)-1,2-propylene glycol to tetrahydrofuran in sequence and stirring evenly; slowly adding magnesium sulfate, stirring and reacting at room temperature for 20 to 25 hours, purifying, and obtaining epoxypyridine; wherein the mass ratio of 2-ethoxypyridine-5-boric acid, 3-(4-glycidylbutoxy)-1,2-propylene glycol, and magnesium sulfate is 1:(1.73 to 1.75):1.5.

[0018] In this scheme, epoxypyridine is a substance obtained by chemically bonding the boric acid group in 2-ethoxypyridine-5-boric acid with the propylene glycol in 3-(4-glycidylbutoxy)-1,2-propylene glycol, so that it has a boron-containing group, a pyridine group and an epoxy group, and is used to modify the binder component and the positive electrode material, effectively increasing the electrical performance and cycle stability.

[0019] Further preferably, the conductive agent includes but is not limited to one or more of acetylene black, Ketjen black, nano-carbon fiber, conductive graphite, and carbon nanotubes; the photoinitiator includes but is not limited to 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone.

[0020] Further preferably, a method for preparing a positive electrode slurry for a lithium ion battery comprises the following steps: uniformly mixing a positive electrode material, a conductive agent, a binder, and a photoinitiator at an orbital speed of 5 to 10 r / min; adding half of the deionized water, stirring for 5 to 10 minutes at an orbital speed of 30 to 40 r / min and a rotational speed of 300 to 350 r / min; adding N-methylpyrrolidone, stirring for 10 to 30 minutes at an orbital speed of 800 to 850 r / min and a rotational speed of 100 to 150 r / min; adding the remaining half of the deionized water, stirring for 1 to 2 hours at an orbital speed of 800 to 850 r / min and a rotational speed of 1300 to 1500 r / min, and vacuum degassing to obtain a positive electrode slurry for a lithium ion battery.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are: in the scheme, epoxy pyridine containing boron groups, pyridine groups and epoxy groups is used to prepare a surface modifier and modified gelatin; then it is used to modify NCM811 particles and added to an adhesive; thereby obtaining a lithium-ion battery positive electrode slurry with excellent electrical properties and cycle stability. DETAILED DESCRIPTION

[0022] The following is a preferred implementation of the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. For ordinary technicians in this technical field, all other embodiments obtained by ordinary technicians in this field without creative work without departing from the principle of the embodiment of the present invention are within the scope of protection of the present invention.

[0023] The preparation method of epoxy pyridine is as follows: 10 parts of 2-ethoxypyridine-5-boric acid and 17.5 parts of 3-(4-glycidylbutoxy)-1,2-propylene glycol are added to 100 parts of tetrahydrofuran in sequence and stirred evenly; 15 parts of magnesium sulfate are slowly added, stirred and reacted at room temperature for 24 hours, and purified to obtain epoxy pyridine; The modified polyvinylidene fluoride is PVDF-g-POEM, and the preparation method is as follows: add 10 parts of polyvinylidene fluoride to 100 parts of N-methylpyrrolidone, stir at 50°C for 0.5 hours, cool to 20°C, add 20 parts of polyethylene glycol methyl methacrylate, 0.05 parts of CuCl catalyst, and 0.4 parts of 4,4'-dimethyl-2,2'-bipyridine; stir for 0.5 hours under nitrogen atmosphere; heat to 90°C and stir for 18 hours, precipitate with methanol, wash, and dry to obtain modified polyvinylidene fluoride; Embodiment 1: A method for preparing a positive electrode slurry for a lithium ion battery, comprising the following steps: Step 1: (1) 10 parts of glucosamine and 22.8 parts of epoxypyridine were added to 120 parts of ethanol in sequence, stirred at 80°C for 8 hours, and purified to obtain a surface modifier; (2) Add 0.32 parts of tetrabutyl titanate to 200 parts of ethanol, add 10 parts of NCM811 particles, disperse evenly by ultrasonication, add a surface modifier aqueous solution (0.1 parts of surface modifier, 10 parts of deionized water), and stir at 40°C for 1.5 hours; stir and evaporate at 60°C until it becomes a paste, freeze-dry, and heat-bake at 80°C for 1 hour to obtain a crude precursor; heat-treat the crude precursor: heat-treat at 500°C for 4 hours in an Ar-3% O2 ​​atmosphere; replace the Ar atmosphere; and then replace the Ar-5% H2 atmosphere and heat-treat at 700°C for 2 hours to obtain a positive electrode material; Step 2: (1) 10 parts of gelatin and 3.6 parts of epoxypyridine are added to 100 parts of ethanol in sequence, stirred at 80°C for 6 hours, purified, and pyridyl gelatin is obtained; 10 parts of pyridyl gelatin are added to 80 parts of PBS solution and stirred evenly, 6.2 parts of methacrylic anhydride are added dropwise, stirred at 40°C for 2 hours, purified, and modified gelatin is obtained; (2) uniformly mixing modified gelatin, modified polyvinylidene fluoride, and polyethylene glycol diacrylate in a mass ratio of 2.5:1.5:0.8 to obtain a binder; Step 3: 38.4 parts of positive electrode material, 4.8 parts of Super P, 4.8 parts of binder, and 0.002 parts of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone are mixed uniformly at a revolution speed of 10 r / min; 15 parts of deionized water are added, and stirred for 10 minutes at a revolution speed of 35 r / min and a rotation speed of 300 r / min; 10 parts of N-methylpyrrolidone are added, and stirred for 30 minutes at a revolution speed of 800 r / min and a rotation speed of 100 r / min; 15 parts of the remaining half of the deionized water are added, and stirred for 1.5 hours at a revolution speed of 800 r / min and a rotation speed of 1500 r / min, and vacuum degassing is performed to obtain a positive electrode slurry for a lithium-ion battery.

[0024] Embodiment 2: A method for preparing a positive electrode slurry for a lithium ion battery, comprising the following steps: Step 1: (1) 10 parts of glucosamine and 22.8 parts of epoxypyridine were added to 120 parts of ethanol in sequence, stirred at 80°C for 8 hours, and purified to obtain a surface modifier; (2) Add 0.32 parts of tetrabutyl titanate to 200 parts of ethanol, add 10 parts of NCM811 particles, disperse evenly by ultrasonication, add a surface modifier aqueous solution (0.1 parts of surface modifier, 10 parts of deionized water), and stir at 40°C for 1.5 hours; stir and evaporate at 60°C until it becomes a paste, freeze-dry, and heat-bake at 80°C for 1 hour to obtain a crude precursor; heat-treat the crude precursor: heat-treat at 500°C for 4 hours in an Ar-3% O2 ​​atmosphere; replace the Ar atmosphere; and then replace the Ar-5% H2 atmosphere and heat-treat at 700°C for 2 hours to obtain a positive electrode material; Step 2: (1) 10 parts of gelatin and 3.6 parts of epoxypyridine are added to 100 parts of ethanol in sequence, stirred at 80°C for 6 hours, purified, and pyridyl gelatin is obtained; 10 parts of pyridyl gelatin are added to 80 parts of PBS solution and stirred evenly, 6.2 parts of methacrylic anhydride are added dropwise, stirred at 40°C for 2 hours, purified, and modified gelatin is obtained; (2) uniformly mixing modified gelatin, modified polyvinylidene fluoride, and polyethylene glycol diacrylate in a mass ratio of 2:1.5:0.5 to obtain a binder; Step 3: Mix 32 parts of positive electrode material, 4 parts of Super P, 4 parts of binder, and 0.002 parts of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone at a revolution speed of 10 r / min; add 12.5 parts of deionized water, stir for 10 minutes at a revolution speed of 35 r / min and a rotation speed of 300 r / min; add 10 parts of N-methylpyrrolidone, stir for 30 minutes at a revolution speed of 800 r / min and a rotation speed of 100 r / min; add 12.5 deionized water, stir for 1.5 hours at a revolution speed of 800 r / min and a rotation speed of 1500 r / min, and vacuum degas to obtain a lithium-ion battery positive electrode slurry.

[0025] Embodiment 3: A method for preparing a positive electrode slurry for a lithium ion battery, comprising the following steps: Step 1: (1) 10 parts of glucosamine and 22.8 parts of epoxypyridine were added to 120 parts of ethanol in sequence, stirred at 80°C for 8 hours, and purified to obtain a surface modifier; (2) Add 0.32 parts of tetrabutyl titanate to 200 parts of ethanol, add 10 parts of NCM811 particles, disperse evenly by ultrasonication, add a surface modifier aqueous solution (0.1 parts of surface modifier, 10 parts of deionized water), and stir at 40°C for 1.5 hours; stir and evaporate at 60°C until it becomes a paste, freeze-dry, and heat-bake at 80°C for 1 hour to obtain a crude precursor; heat-treat the crude precursor: heat-treat at 500°C for 4 hours in an Ar-3% O2 ​​atmosphere; replace the Ar atmosphere; and then replace the Ar-5% H2 atmosphere and heat-treat at 700°C for 2 hours to obtain a positive electrode material; Step 2: (1) 10 parts of gelatin and 3.6 parts of epoxypyridine are added to 100 parts of ethanol in sequence, stirred at 80°C for 6 hours, purified, and pyridyl gelatin is obtained; 10 parts of pyridyl gelatin are added to 80 parts of PBS solution and stirred evenly, 6.2 parts of methacrylic anhydride are added dropwise, stirred at 40°C for 2 hours, purified, and modified gelatin is obtained; (2) uniformly mixing modified gelatin, modified polyvinylidene fluoride, and polyethylene glycol diacrylate in a mass ratio of 2.5:1.5:1 to obtain a binder; Step 3: 40 parts of positive electrode material, 5 parts of Super P, 5 parts of binder, and 0.0025 parts of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone are mixed uniformly at a revolution speed of 10 r / min; 17.5 parts of deionized water are added, and stirred for 10 minutes at a revolution speed of 35 r / min and a rotation speed of 300 r / min; 12 parts of N-methylpyrrolidone are added, and stirred for 30 minutes at a revolution speed of 800 r / min and a rotation speed of 100 r / min; 17.5 parts of deionized water are added, and stirred for 1.5 hours at a revolution speed of 800 r / min and a rotation speed of 1500 r / min, and vacuum degassing is performed to obtain a positive electrode slurry for a lithium ion battery.

[0026] Based on Example 1, a control experiment was carried out, specifically Comparative Examples 1 to 5, as described below: Comparative Example 1: Based on Example 1, the positive electrode material was adjusted, and NCM811 particles were used as the positive electrode material; the specific changes were: Step 3: 38.4 parts of NCM811 particles, 4.8 parts of Super P, 4.8 parts of binder, and 0.002 parts of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone are mixed uniformly at a revolution speed of 10 r / min; 15 parts of deionized water are added, and stirred for 10 minutes at a revolution speed of 35 r / min and a rotation speed of 300 r / min; 10 parts of N-methylpyrrolidone are added, and stirred for 30 minutes at a revolution speed of 800 r / min and a rotation speed of 100 r / min; 15 parts of the remaining half of the deionized water are added, and stirred for 1.5 hours at a revolution speed of 800 r / min and a rotation speed of 1500 r / min, and vacuum degassing is performed to obtain a lithium-ion battery positive electrode slurry.

[0027] Comparative Example 2: Based on Example 1, the surface modifier was adjusted, and glucosamine was used as the surface modifier; the specific changes were: Step 1: Add 0.32 parts of tetrabutyl titanate to 200 parts of ethanol, add 10 parts of NCM811 particles, disperse evenly by ultrasonication, add glucosamine aqueous solution (0.1 parts of glucosamine, 10 parts of deionized water), and stir at 40°C for 1.5 hours; stir and evaporate to a paste at 60°C, freeze-dry, and heat-bake at 80°C for 1 hour to obtain a crude precursor; heat-treat the crude precursor: heat-treat at 500°C for 4 hours in an Ar-3% O2 ​​atmosphere; replace the Ar atmosphere; and then replace the Ar-5% H2 atmosphere and heat-treat at 700°C for 2 hours to obtain a positive electrode material.

[0028] Comparative Example 3: Based on Example 1, no surface modifier is introduced; the specific changes are: Step 1: Add 0.32 parts of tetrabutyl titanate to 200 parts of ethanol, add 10 parts of NCM811 particles, disperse evenly by ultrasonication, add 10 parts of deionized water dropwise, and stir at 40°C for 1.5 hours; stir and evaporate to a paste at 60°C, freeze-dry, and heat-bake at 80°C for 1 hour to obtain a crude precursor; heat-treat the crude precursor: heat-treat at 500°C for 4 hours in an Ar-3% O2 ​​atmosphere; replace the Ar atmosphere; then replace the Ar-5% H2 atmosphere and heat-treat at 700°C for 2 hours to obtain a positive electrode material.

[0029] Comparative Example 4: Based on Example 1, the binder was adjusted and PVDF was used as the binder; the specific changes were: Step 3: 38.4 parts of positive electrode material, 4.8 parts of Super P, 4.8 parts of PVDF, and 0.002 parts of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone are mixed uniformly at an orbital speed of 10 r / min; 15 parts of deionized water are added, and stirred for 10 minutes at an orbital speed of 35 r / min and a rotation speed of 300 r / min; 10 parts of N-methylpyrrolidone are added, and stirred for 30 minutes at an orbital speed of 800 r / min and a rotation speed of 100 r / min; 15 parts of the remaining half of the deionized water are added, and stirred for 1.5 hours at an orbital speed of 800 r / min and a rotation speed of 1500 r / min, and vacuum degassing is performed to obtain a positive electrode slurry for a lithium-ion battery.

[0030] Comparative Example 5: Based on Example 1, the modified gelatin in the binder was adjusted to modify the gelatin with a single methacrylic anhydride; the specific changes were: Step 2: (1) Add 10 parts of gelatin to 80 parts of PBS solution and stir evenly, add 6.2 parts of methacrylic anhydride dropwise, stir and react at 40°C for 2 hours, purify, and obtain modified gelatin; (2) Mix modified gelatin, modified polyvinylidene fluoride, and polyethylene glycol diacrylate in a mass ratio of 2.5:1.5:0.8 to obtain a binder.

[0031] In the above embodiments, the number of parts is by mass; the purchase manufacturers of all the raw materials involved are not subject to any special restrictions, and exemplary examples include: the NCM811 particles have a product number of PA91222, purchased from Wengjiang Reagent; Super P model SP, purchased from Yibo Rui; the specification of polyvinylidene fluoride is ≥99.5%, purchased from Shenzhen Kejing; gelatin is type A gelatin, the product number is SY0516, purchased from Biolab; the CAS number of polyethylene glycol diacrylate is 26570-48-9; the CAS number of methacrylic anhydride is 760-93-0; the CAS number of glucosamine is 3416-24-8; the CAS number of polyethylene glycol methyl methacrylate is 26915-72-0; the CAS number of 2-ethoxypyridine-5-boric acid is 612845-44-0; the CAS number of 3-(4-glycidylbutoxy)-1,2-propylene glycol is 139471-23-1; all are commercially available.

[0032] Testing experiment: The positive electrode slurry of lithium-ion battery prepared in the embodiment and comparative example was evenly coated on aluminum foil, and the surface density of active material was 1.1 mg / cm 2; Irradiate under ultraviolet light (light source is 1000W, illumination distance is 20cm) for 30 seconds, vacuum dry at 80℃ for 6 hours; after rolling, vacuum dry at 110℃ for 12 hours to obtain the positive electrode. And use metal lithium sheet as negative electrode, Celgard2400 film as diaphragm, 1mol / L LiPF6 solution as electrolyte (solvent is EC and DMC with volume ratio of 1:1) to assemble into CR2016 button battery. At 60℃, with a voltage range of 3~4.3V, after 1 cycle at 0.1C, the charge and discharge performance is tested at a current density of 1C to obtain the initial defense line specific capacity, and cycle 60 times, test again, and calculate the cycle efficiency; the data obtained are shown in the following table: sample Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Initial discharge specific capacity (mAh / g) 199.36 198.84 199.12 192.64 194.50 195.87 195.27 196.73 Cycle efficiency (%) 95.69 95.32 95.56 65.89 87.09 83.69 88.56 90.25 Conclusion: In this application, NCM811 is modified to form a thermal stability protective layer on its surface, thereby effectively improving the stability of the positive electrode material under high temperature cycles and inhibiting the corrosion cracking and the substantial increase in internal resistance. At the same time, in the scheme, the bonding stability is effectively improved by a binder with specific components, and the de-powdering and coating shedding are reduced, thereby effectively improving the cycle stability of the electrical performance and increasing safety. The data in Comparative Examples 1 to 5 prove that the modification of NCM811 particles by a carbon dioxide precursor containing a surface modifier can effectively improve the electrical performance and cycle stability. The adhesive containing modified gelatin can effectively improve the electrical performance and cycle stability because it improves the bonding stability and electron mobility of the positive electrode material.

[0033] Finally, it should be noted that the above is only a preferred embodiment of the present invention, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the spirit and principle of the present invention and within the technical scope disclosed in this application should be included in the protection scope of this application; in the absence of conflict, the embodiments of this application and the features in the embodiments can be combined with each other. Therefore, the protection scope of this application shall be based on the protection scope of the claims.

Claims

1. A positive electrode slurry for a lithium ion battery, characterized in that: The positive electrode slurry of the lithium ion battery comprises the following components: by weight, 32 to 40 parts of positive electrode material, 4 to 5 parts of conductive agent, 4 to 5 parts of binder, 0.002 to 0.0025 parts of photoinitiator, 25 to 35 parts of deionized water, and 10 to 12 parts of N-methylpyrrolidone.

2. A lithium ion battery positive electrode slurry according to claim 1, characterized in that: The preparation method of the positive electrode material comprises the following steps: adding tetrabutyl titanate to ethanol, adding NCM811 particles, uniformly dispersing by ultrasonication, adding a surface modifier aqueous solution, stirring at 40-45°C for 1-2 hours; stirring and steaming at 60-65°C to a paste, freeze-drying, and heating at 70-80°C for 1-2 hours to obtain a crude precursor; and heat-treating the crude precursor to obtain a positive electrode material.

3. A lithium ion battery positive electrode slurry according to claim 2, characterized in that: The raw materials of the crude precursor include the following components: 10 parts of NCM811 particles, 0.3-0.35 parts of tetrabutyl titanate, 160-200 parts of ethanol, 0.1-0.12 parts of a surface modifier, and 8-12 parts of deionized water.

4. The positive electrode slurry for lithium-ion batteries according to claim 2, characterized in that: The heat treatment process is: heat treatment at 500-600°C for 4-5 hours in an Ar-3% O2 ​​atmosphere; replacing the Ar atmosphere; and then replacing the Ar-5% H2 atmosphere with heat treatment at 680-700°C for 2-3 hours to obtain the positive electrode material.

5. The positive electrode slurry for lithium-ion batteries according to claim 3, characterized in that: The preparation method of the surface modifier comprises the following steps: adding glucosamine and epoxypyridine to ethanol in sequence, stirring and reacting at 78-82° C. for 6-8 hours, and purifying to obtain the surface modifier; wherein the mass ratio of glucosamine to epoxypyridine is 1:(2.25-2.3).

6. The positive electrode slurry for lithium-ion batteries according to claim 1, characterized in that: The binder comprises modified gelatin, modified polyvinylidene fluoride and polyethylene glycol diacrylate in a mass ratio of (2-2.5):1.5:(0.5-1); the modified polyvinylidene fluoride is PVDF-g-POEM.

7. A lithium-ion battery positive electrode slurry according to claim 6, characterized in that: The preparation method of modified gelatin comprises the following steps: (1) adding gelatin and epoxy pyridine to ethanol in sequence, stirring and reacting at 78-82° C. for 6-8 hours, purifying, and obtaining pyridyl gelatin; (2) adding pyridyl gelatin to phosphate buffer solution and stirring evenly, adding methacrylic anhydride dropwise, stirring and reacting at 40-45° C. for 2-3 hours, purifying, and obtaining modified gelatin; Among them, the mass ratio of gelatin and epoxy pyridine is 1: (0.35~0.4); in the modified gelatin, the mass ratio of pyridyl gelatin and methacrylic anhydride is 1: (0.6~0.65).

8. A positive electrode slurry for lithium-ion batteries according to any one of claims 5 or 7, characterized in that: The preparation method of epoxy pyridine comprises the following steps: adding 2-ethoxy pyridine-5-boric acid and 3-(4-glycidyl butoxy)-1,2-propylene glycol to tetrahydrofuran in sequence and stirring evenly; slowly adding magnesium sulfate, stirring and reacting at room temperature for 20 to 25 hours, purifying, and obtaining epoxy pyridine; wherein the mass ratio of 2-ethoxy pyridine-5-boric acid, 3-(4-glycidyl butoxy)-1,2-propylene glycol and magnesium sulfate is 1:(1.73 to 1.75):1.

5.

9. The positive electrode slurry for lithium-ion batteries according to claim 6, characterized in that: The conductive agent includes one or more of acetylene black, Ketjen black, nano-carbon fiber, conductive graphite, and carbon nanotubes; and the photoinitiator includes 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone.

10. The method for preparing a positive electrode slurry for a lithium ion battery according to claim 1, characterized in that: The method comprises the following steps: uniformly mixing a positive electrode material, a conductive agent, a binder and a photoinitiator at a revolution speed of 5-10 r / min; adding half of the deionized water, stirring for 5-10 minutes at a revolution speed of 30-40 r / min and a rotation speed of 300-350 r / min; adding N-methylpyrrolidone, stirring for 10-30 minutes at a revolution speed of 800-850 r / min and a rotation speed of 100-150 r / min; adding the remaining half of the deionized water, stirring for 1-2 hours at a revolution speed of 800-850 r / min and a rotation speed of 1300-1500 r / min, and vacuum degassing to obtain a positive electrode slurry for a lithium ion battery.